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All in one valve

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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All in one valve

Unread postAuthor: john bunsenburner » Sat Feb 20, 2010 5:25 am

The search for a semi-automatic valve has continued for a long time. Several members on this forum have made advancements in the area producing more and more valves which are capable of functioning semi-automatically feasibly.
Based on many previous designs(I would like to point out especially Poland_Spud's ideas have helped me a lot, though other members' ideas have contributed to this idea too), I designed a valve which incorporates all aspects needed for semi automatic function in one compact block of material. I hoped to give the forum a working example before 2010 however found that my agenda was too full and thus have not yet finished the build. Nonetheless I uploaded an animation of the valve's function. The animation is fairly self explanatory(and I thank JSR for the help in making it), and I am happy to receive all criticism, advice and opinions on the valve.
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semi-auto mech.gif
semi-auto mech.gif (18.86 KiB) Viewed 1432 times
Last edited by john bunsenburner on Sat Feb 20, 2010 10:27 am, edited 1 time in total.
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Unread postAuthor: Crna Legija » Sat Feb 20, 2010 6:47 am

nice what make the orange bit move? a solenoid?

what program do you use to make animations?
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Unread postAuthor: john bunsenburner » Sat Feb 20, 2010 7:42 am

With smaller calibers i think the rod can moved by a trigger, this is what I am planning to do in my design which uses 6mm steel bbs. With larger calibers an alternative must be found as the required trigger movement to move the rod the distance required is not feasible.

To make the animation I used Jasc Animation Shop 3 making the frames using MS Paint.
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Unread postAuthor: Demon » Sat Feb 20, 2010 7:51 am

To make full auto, you could connect the orange rod to a cylinder and the other side to a spring connected to the main chamber ...

Looks great, and a such valve could be pretty small .
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Unread postAuthor: jackssmirkingrevenge » Sat Feb 20, 2010 8:51 am

Nice to see you got the hang of animations :)

I've long thought of making a sliding block design, here's one I had come up with using an eccentric cam to operate it for full/semi auto:

Image

The need for perfect sealing always put me off though.
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Unread postAuthor: mark.f » Sat Feb 20, 2010 9:56 am

Looks like a workable concept, john, but where are the O-rings on the rod. :wink:

Other than that, I think it will work. If you wanted to get fancy with larger designs, you could use pneumatic cylinders to actuate the rod.
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Unread postAuthor: john bunsenburner » Sat Feb 20, 2010 10:08 am

Its nice to know I'm not alone with my concept, as they say "great minds..." I'll spare you the rest.

Now the sealing problem is a large one, though I assume the problem could some how be solved. Insomniac suggested I use a concept similar to that used in boats for sealing around the propellor shaft, called a stuffing box. It uses a tight fitting shaft and grease to make a seal. I am sure with low pressures and a large distance between ports, along with very tightly fitting parts this could be used my design too.

As for the O-rings, i thought they were so obvious that everyone would imagin them there, but as you point it out, I'll go put them in.
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Unread postAuthor: POLAND_SPUD » Sat Feb 20, 2010 11:53 am

that's a pretty good idea

criticism...
you should try to achieve the highest speed of the rod/spool as possible to achieve short opening time but then it must stop instantly.. though I think it can be worked out somehow


I've just noticed something... if you want to use orings all the ports have to be on different levels... meaning that they cannot face each other as air can leak around the spool

this means that your valve would have to look exactly like any DCV spool valve

look here clicky (it's in a .doc file... have a look at the pic showing a 3 way valve there)

A couple of months ago I drew this
Imageas you can see this was only the main valve but I am sure you could find a way to incorporate a simple loading T + air cylinder there


you could use pneumatic cylinders
yeah I agree that would simplify a lot...
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valve+loadingmech.PNG
this is a slight mod of that design..

I know it should be easier to machine than the design I mentioned in my other post and still keeps all the advantages of that one... uhmm let's jsut say that's one of my alternative designs
valve+loadingmech.PNG (28.86 KiB) Viewed 1395 times
Last edited by POLAND_SPUD on Sat Feb 20, 2010 1:14 pm, edited 1 time in total.
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Unread postAuthor: john bunsenburner » Sat Feb 20, 2010 1:00 pm

I did not notice that, but it can be avoided, thoguh it makes the design more complex , which I wish to avoid. As for the speed, please consider the O-ring inside the ammunition compartment within the spool. The O-ring here prevents air to flow before the projectile clears the compartment fully, which only happens when the right position is reached. Thus the discharge will be very fast and the valve rather efficient.

I assume using a gas cylinder would simplify matters, but really I am looking for a solution with few moving parts, which can be constructed quickly and easily and is not pricy. Though a gas cylinder could be made for little money it makes manufacteur of the valve a fair bit longer and also increases moving parts, which means more can go wrong(especially with a hydrolic/pneumatic cylnder which needs to be leak free, this is always a problem to achieve) and so I would rather avoid using pneumatic cylinders and the like.


After another little think a while back I though the following may just be a better idea. Instead of a spool that moves up or down, it rotates instead. It has advantages, such as I can keep it in a closed system(less worry about leaking to the out side), with only one O-ring to seal against the atmosphere where the spool attaches to some sort of triggering mechanism. This is a rather crude idea, but really I am in the search of a simple "All in one" valve, and bouncing ideas back and forth is always very productive.
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semiauto mech 2.gif
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Unread postAuthor: POLAND_SPUD » Sat Feb 20, 2010 1:34 pm

that first design wasn't so bad but you have to seal it somehow... if you use orings there will be a small bap between the spool and the housing and air could flow through that gap...
that's infact how all the DCV spool valves work.. air is free to flow around the spool but not through o-rings that's why the ports have to be on different levels so to speak

you could try to seal it without orings... more less in the same way as the DCV valve that I use on the MKIII...

the valve has no seals as the spool is machined very precisely so that it's OD is very close to the ID of the housing where it moves.. with a bit of oil it seals perfectly

though it all comes down to whether you can machine it so precisely


Instead of a spool that moves up or down, it rotates instead
I think it would be more difficult to seal it and switching the valve would be slightly more difficult too...

when you've got a valve that moves up and down all you need is to use an air cylinder and a small 3 way valve (both of which can be bought from ebay for under ~15$) and you've got a pretty good and compact way to switch the valve
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Unread postAuthor: john bunsenburner » Sat Feb 20, 2010 5:16 pm

Its a pitty the original desin would not work, but it seemed just a little too simple...

I assume that with a VERY tight fitting spool and heavy grease i can surely get it to work. The question until what pressure is one left to be answered.

Perhaps with very high pressure applications the entire system could be put into a bath of heavy oil or grease, so that the leaks are really reduced to a minimum.
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Unread postAuthor: POLAND_SPUD » Sat Feb 20, 2010 6:04 pm

well you could always try the idea I posted here... I think this could be built using only a drill press .. the spool could be built from a threaded rod, nuts and washers with o-rings in between
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Unread postAuthor: iknowmy3tables » Sat Feb 20, 2010 8:44 pm

is it really that hard to come up with these designs
why are you so persistent on a elevator mechanism,
also rotating valve have been mention many times before but no one has figgured out how to make one, if you can actually construct one then I applaud you
note in your designs it probably would be best if the valve were not opened until the the projectile can exit the barrel other wise you would waste air
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integratedsujestion1.PNG
why are you so fixed on elevator designs, when classic bolt designs work
integratedsujestion1.PNG (24.71 KiB) Viewed 1312 times
integratedsujestion4.PNG
but if you insist you can just turn a bolt design 90 degrees
integratedsujestion4.PNG (20.16 KiB) Viewed 1312 times
integratedsujestion2.PNG
how about a sliding barrel design
integratedsujestion2.PNG (37.98 KiB) Viewed 1312 times
integratedsujestion3.PNG
or if you can manage to do orings grooves in the walls you try designs like this
integratedsujestion3.PNG (13.34 KiB) Viewed 1312 times
integratedsujestion5.PNG
if you can make rotating valves then there are worlds of potential
integratedsujestion5.PNG (17.88 KiB) Viewed 1312 times

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Unread postAuthor: POLAND_SPUD » Sat Feb 20, 2010 9:42 pm

lol you've just missed what I've mentioned in two posts.. ports can't be on the same level

anyway apart from that nice drawings... do you plan to build any of them ?


the more I look at the design I modified here the more I like...

the valve itself does not load ammo... there is an air cylinder to do this... for some reasons it might be better to have a separate valve and loading mech. but both of them are still housed inside one part... also notice that this design does not require much precision...

is there anything wrong with it that I missed?
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Unread postAuthor: Marffy » Sat Feb 20, 2010 10:04 pm

i like the design. maybe you could have some sort of trigger mechanism that pulls the "piston" up. how many PSI would you use on something like this?
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